In Japanese Patent Publication No. H10-203338, a brake-by-wire vehicle brake control device is proposed which has four pumps respectively for the four wheels of a vehicle. Two of the four pumps are located in a common conduit path for two of the four wheels and are driven by a common motor. The other two of the four pumps are located in another common conduit path for the other two of the four wheels and are driven another common motor.
In the vehicle brake control device, a detection signal from a depression force sensor is inputted to a brake ECU when a depression force is applied to a brake pedal, which is an example of a brake operating member. On detecting the depression force, the brake ECU device drives the motors to activate the pumps. The pumps accordingly draw in and discharge brake fluid that is in a tank and generate a wheel cylinder pressure (hereinafter referred to as the “W/C pressure”). The brake ECU controls according to the applied depression force the amount of opening of a variable orifice provided for each of the wheels, thereby adjusting the W/C pressure such that the adjusted W/C pressure becomes appropriate for the detected depression force.
However, in the vehicle brake control device configured as described above, a mechanical connection is completely severed between the depression force on the brake pedal and supply of brake fluid from the tank. Therefore, any fail-safe measure which generates a braking force even if some sort of abnormality occurs in the vehicle brake control device inevitably depends on control performed by the brake ECU. To guarantee reliability of the fail-safe measure, every type of control by the brake ECU must be made more complicated, which is not desirable.